1. Field of the Invention
The present invention relates to a data coupler, and more particularly, to a data coupler to perform communication using an electric power line.
2. Description of the Related Art
Various data couplers to couple data between an electric power line and a communication device, such as a modem, have been used as data communication systems using electric power lines. For example, a data coupler including an inductive coupler that includes an electric power line conductor as a primary winding, a capacitor connected across a secondary winding of the inductive coupler to create a resonant circuit with the secondary winding at a frequency within a desired frequency band, and an impedance matching transformer to connect a communication device to the secondary winding is disclosed in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2006-503504.
In the data coupler, a parallel resonant circuit is defined by providing a transformer on an electric power line and inserting a capacitor on a side of the transformer near a secondary winding, and the resonant frequency of the parallel resonant circuit is set to substantially the same frequency as the frequency of a radio-frequency signal used for data exchange. Accordingly, a radio-frequency signal to be used for data exchange is acquired and transmitted to a modem or other suitable component that performs data processing.
However, since an alternating current of about 100 V from an electric power line must flow in this type of data coupler, use of a copper wire that withstands high power is required. Thus, there is a problem in that the size of the coupler itself must be increased. In addition, since a data coupler must be directly connected to an electric power line, there is another problem in that it is difficult to install the data coupler onto the electric power line.